Proportional compasses for per



J. H. A. MIALARET.

PROPORTIONAL COMPASSES FOR PERSPECTIVE DRAWING.

APPLICATION FILED MAY I6. 1914.

1 19,8914. PatentedAug. 8,1916.

L EgEQLE WHNESSES iNENWR AEWRNEY pniann sra'rns rn rnn r nation J'OHANNES I-IUBER'I ANTON MIALARET, OF MAASTRIGHT, NETHERLANDS.

PROPOBTIONAL COMPASSES FOR PERSPECTIVE DRAWING.

Application filed May 16, 1914.

To all whom it may concern.

.Be it known that I, JoHANNEs HUBERT ANTON MIALARET, a subject of the Queen of the Netherlands, and residing at 11 Breede straat, Maastricht, the Netherlands, have invented certain new and useful Proportional Compasses for Perspective Drawing, of which the following is a specification.

This invention relates to proportional or reducing compasses for perspective drawing, by which from a given plan and elevation, a perspective drawing can be made without any calculation being required therefog. The compasses comprise two pairs of legs movable in the manner of shears; according to the present invention the length of the individual legs can be varied independently of each other.

The proportional compasses according to this invention and their application in practice are illustrated on the accompanying drawing.

Figures 13 show problems in perspectivedrawing which can be solved with the (LC so so Specification of Letters Patent.

Patented Aug. 8, 1916.

Serial N0..839,063.

proportional compasses according to this invention without any calculation being required. Figs. 4; and 5 represent respectively a side elevation and a front elevation of the proportional compasses when closed. Fig. 6 represents one body piece of the compass looking at the inner face, with leg extended. Fig. '7 is a cross section according to the line V-l/V in Fig. 5.

In Fig. 1 a shed or barn is shown, which is to be drawn on the vertical picture plane P P. S is the center of projection or the point of sight, C the center of the picture or the center of Vision, H H the horizontal plane through the eye and D D the plane dividing the infinite space for the spectator in a right hand portion and a left hand portion. A is assumed to be a point in the height of the eye on the wall edge B F of the shed, A Y a perpendicular drawn from A upon the plane D D and a the perspective of the point A. C Y then is the distance of A behind the picture plane and it may be determined from the following formula:

distance of the eye from the picture plane A Y sY SC+CY distance of the eye from the picture plane+distance of the point behind the picture plane.

Calling the distance of the eye from the picture plane D (hereinafter shortly referred to as distance) and the distance behind the picture plane P" (hereinafter shortly referred to as depth), the foregoing proportion will be equal to Al Di+Pr Upon this proportion, which gives the reduction for a straight line parallel to the picture plane, the practical use and arrangement of the proportional compasses according to the present invention is based. For each portion of the same straight line parallel to the picture plane there will be the same reduction, the latter, however, being different for each other parallel line in accordance with the varying distance behind the picture plane or depth.

In Fig. 2 the plan and elevation of the shed shown in Fig. 1 are drawn, hereafter a perspective drawing (see Fig. 3) is to be made. In Fig. 2, G G is the ground-line of an assumed picture plane, C the projection of an assumed center of the picture upon G G and C D the trace f the. dividi g plane D D. The lines G G and C D then can serve for measuring for each point in the plan the distance behind the picture plane and the distance to the right or to the left from D D.

In the elevation the assumed horizon H H can serve for measuring for every point the height above or depth under the horizon.

After having chosen a certain length D for the distance, the perspective of the shed could be determined by calculation. For this purpose first the lines H H and D D (see Fig. 3) are drawn, thereupon the length of the line C, a, is calculated by reducing the length of the line A Y of Fig. 2 according to the proportion (in this case thus This .calculated length is set off from C to the right on H H, thereby obtaining the point a Now drawing a perpendicular through a and setting off the lines A B, A F and A E from Fig. 2 reduced in the same proportion as A Y from a on said perpendicular, the required points 6, f and c of the wall edge 6 2 ill be btained.

In a similar way for each other wall edge the perspective reducing could be determined by calculation; hereby the reducing proportion D i-P varies for each different depth.

The present invention now has for its object to replace the calculation of these re- I ducing proportions by a simple mechanical reduction. Nhen of a pair of proportional compasses one pair of legs the length D and the other pair of legs the length DH-P" is given (see Fig. 2), then all distances taken between the points of the longer pair of legs will be reduced according to the proportion Di Di+Pr between the points of the shorter pair of legs. With such proportional compasses the reductions otherwise to be calculated can thus be determined by a simple mechanical operation.

In Figs. 2 and 3 this is shown for the line A F. One pair of legs of the compasses is made equal to D and the other pair equal 'to DH-P". Between the points of the longer pair of legs the line A F from Fig. 2 is taken; between the shorter pair of legs this line is reduced according to the proportion l Di+Pr thus giving the perspective length a f. This length is set off in Fig. 3, after having previously ascertained the point a from C out by reducing A Y According to this invention the legs of the proportional compasses are arranged in such away that the lengths of the individual legs can be varied independently of each other.

In the embodiment of the invention shown in Figs. 44 the compasses consist of two body pieces I, pivotally connected by means of a screw R with wing nut T and pressure spring U. Each body piece is provided with two slidable legs J and K. On the legs J (the distance legs) the distance D and on the legs K (the depth legs) the length DH-P is set ofi. By employing a tube L or other telescoping means, the legs K can obtain a considerably greater length than the legs J. One of the body pieces I moreover contains an adjustable distance indicator M for the purpose of indicating from the pivot of the compasses the distance D on one of the legs K. The distance indicator is provided with a plurality of center holes O and at its outer extremity with a center hole N, the distance between the pivot of the compasses and said center hole N being made equal to the distance. From this center hole N now the depth P is added upon the legs K. The telescoping tubes L and the lower slidable legs J are secured in the required position by means of the screws 4, and the legs K which slide within the tubes L are secured therein by the screws 5.

As stated hereinbefore by perspective drawing the reducing proportion continually varies with the changing of the depth 1 the distance D however, always remaining unchanged for the same drawing. WVith the distance indicator now the advantage is obtained that the Varying reducing proportion can in a very simple way be fixed by every time setting off the changed depth from the center hole N upon the legs K.

The groove containing the distance indicator is provided'with a slot on the inside of the body piece I, so that in case of a short distance one of the center holes 0 may be used instead of the center hole N. The distance indicator M is further provided with a g or inch scale.

The inside view (Fig. 6) shows a number of engraved division lines for the purpose of enabling the setting out of the distance on the legs J and on the distance indicator M from the inaccessible pivot of the compasses.

The body pieces. I are provided with a number of holes Q, each of which may be used as pivot hole for the compasses. In this way the range of the compasses is enlarged, which is of importance 6. 9. when the object to be drawn is located far behind the ground line.

The setting off of a dimension such as A Z of Fig. 2 from the center hole N on a depth leg K of the compasses may be eflected by means of ordinary compasses.

In case the plans are, however, of such a size that the depth legs K cannot be made sufliciently long for the depth dimensions then the taken dimension is every time set off in a reduced state, thereby employing ordinary reducing compasses as auxiliary compasses. In such cases a simple reduction is chosen, such as 3;, etc., whereby the distance legs J too are then to be adjusted for T}, etc., of the distance. In this way the legs of the compasses will have the correct proportion again for setting out the dimensions in the picture.

When the dimension of the assumed distance surpasses the greatest possible or de sirable length of the distance legs J of the compasses suitable reductions such as or the like are similarly employed.

In very small plans such as may for example be found in books the distance and the depth are by means of such auxiliary compasses set off on the legs J and K in an enlarged scale.

Such auxiliary compasses, serving to make the proportional compasses according to this invention adapted for all practical purposes and thus for drawings of the most varying sizes, may be of a very simple construction, as said compasses, .though they must be of a somewhat large size, are to reduce or to enlarge in a few fixed proportions only.

The proportional compasses for perspective drawing may be of any suitable construction provided that the length of one pair of legs can be made equal to the dimension of the distance and the length of the other pair equal to the dimension of the distance plus the depth.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is 1. Proportional compasses for perspective drawing comprising, in combination, two body pieces, a screw and nut for pivotally connecting said body pieces together, two pairs of legs one of each pair being slidably contained in each body piece, and means for locking the individual legs after they have been adjusted, independently of each other.

2. Proportional compasses for perspective drawing comprising, in combination, two body pieces, a screw and nut for pivotally connecting said body pieces together, each of said body pieces having a. plurality of holes adapted to receive the pivot of the compasses, two pairs of legs one of each pair being slidably contained in each body piece, and means for locking the individual legs after they have been adjusted, independently of each other.

3. Proportional compasses for perspective drawing comprising, in combination, two body pieces, a screw and nut for pivotally connecting said body pieces together, two pairs of legs one of each pair being slidably contained in each body piece, a distance indicator slidable in one body piece for indicating the distance from the pivot of the compasses on the leg contained in that body piece and means for locking the individual legs after they have been adjusted, inde pendently of each other.

a. Proportional compasses for perspective individual legs after they have been adjusted, independently of each other.

Proportional compasses for perspective drawing comprising in combination two body pieces one of which is provided with a groove and a slot on the inside in connection with the groove, a screw and nut for pivot ally connecting the said body pieces together, two pairs of legs one of each pair being slidably contained in each body piece, a distance indicator slidable in the groove, and having a center hole on the outer extremity also having a plurality of center holes visible through the slot and whichare adapted to be employed instead of the center hole on the outer extremity of the distance indicator for setting off a given dimension (the distance from the point to be projected to the picture plane) on one of the legs, and means for locking the individual legs after they have been adjusted, inclependently of each other.

6. Proportional compasses for perspective drawing comprising, in combination, two body pieces, a. screw and nut for pivotally connecting said body pieces together, each of said body pieces having a plurality of holes and scale marks, and one of said body pieces being provided with a groove and a slot in the inside, two pairs of legs, a distance indicator slidable inside the groove, and provided with scale marks and having a center hole on its outer extremity, also having a plurality of center holes equidistantly arranged over its length, and means for locking the individual legs after they have been adjusted, independently of each other.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

J OHANNES HUBERT ANTON MlALARE'l.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. C. 

